Telephone system.



l. L. McQU ARRIE & C. L. GOODRUM.

TELEPHONE SYSTEM.

APPLICATION FILED NOV. 2|. lgu.

1,298,237. Pawnted Mar. 25,1919.

2 SHEETS-SHE 2.

4.9 5/ 'f i1- 1% K /n en/ans.- James L. M auarr ic Charles L. 6aa 3-um.

' countyof Essex and UNITED STATES PATENT OFFICE.

JAMES L. MOQU ABRIE, OF MON'ICLAIR, NEW JERSEY, AND CHARLES L. GOODRUM, OF: NEW YORK, N. Y.,-ASSIGNOBS TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE SYSTEM.

Specification of Letters Patent.

Patented Mar. 25, 1919.

Application filed November 21, 1917. Serial No. 203,092.

To all whom'z't may concern:

Be it known that W8,JAMES L. MGQUARBIE and CHARLES L. GoonnUM, citizens of the United States, residin' at Montclair, in the tate of New Jersey, and at New York, in the county of New York and State of New York, respectively, have invented certain new and useful Improvements in Telephone Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone systems employin machine switching apparatus for establishing connections, and more particularly to the circuit arrangement for controlling the operation of the switching apparatus.

In a copending application of J. L. Mc- Quarrie', Serial No. 203,971, filed November 26, 1917, there is shown and dscrilmd a switch structure in which a. plurality of selectively operable step-by-step switches are arranged in a group and rovided with a plurality of master actuating mechanisms, common to all the switches of the group, and with means for -'operatively associating any one of these mechanisms with any one of the switches.

An object of the present invention is the provision of circuits and means, to be used in connection with switches of the character described in the above mentioned application, whereby a switch will test-busy either when engaged in extending a connection, or

when idle and there is no common master mechanism operativel associated therewith.

Another object is the provision of means whereby a master device, in its search for an idle switch of the group, is capable of discriminating between switches which have some other master device allotted thereto and those 'which have not, thus preventing more than one of such devices becoming associated with a switch at the same time.

Still another feature consists in circuit means for controllin the operation of the release mechanism, w ich is common to the group of switches, and in such a manner that said mechanism is capable of positioning itself before and releasin any switch that is found in proper condition to be returned to normal.

These and other objects will be morevention for controlling the operation of the.

switches shown in Fig. 1.

Referring to Fig. 1, a group of switch shafts 1 are each provided with a plurality of vertical anda'otary stepping ratchets and 3. Fixed to the upper end of each shaft is a set of brushes 4, 5 and arranged to be elevated into operative relation to any level in the bank 7 by shaft 1, and thereupon rotated onto a desired set of terminals in such love]. A number of worm members 8, one for each set of vertical and rotary ratchets 2 and 3, are disposed parallel to one another adjacent to the switch shafts 1. The surface of these worms is provided with an endless spiral slot or groove 9. Attached to the end" of each worm is a drivingratchet 10. A

drive magnet 11, having an armature 12 and pawl 13, serves, when energized, to rotate worm 8 in its bearings (not shown).

A supporting frame 14 is loosely mounted" upon each of the endless worms 8, and is provided with any suitable means for engaging the slot thereof, whereby rotation of such worm causes frame 14 to move back and forth before switch shafts 1. Frame 14 is also slidably mounted upon a pair of sta tionary rods 15, which accurately guide said frame in its movement from position to position. A mounting bracket 16 secured to the frame 14 supports the primary or vertical stepping magnet 17. Magnet 17 has an armature 18, iVota-lly attached to frame 14 with its working end. provided with a stepping p'awl so arranged as to engage and operate the vertical ratchet 2 when the master device is positioned before a switch shaft 1. 'A secondary or rotary stepping magnet 19 is also mounted on the frame'14 and likewise has an armature adapted to' engage and r0- tate shaft 1 through the medium of rotary ratchet 3. The lower portion of the frame 14 is turned under to f rm a supporting table 0, upon which a magnet 21 is mounted. Sai magnet has an arnla ure 22, pivoted to frame 14, and extending into cooperative relation with the pins 23 of vertical rods 24, whereby energization of the magnet, when frame 14 is positioned before a shaft 1, causes rod 24 to be moved downward against the end of a lever 25. Secured to frame 14 are two pins 26 and 27, the former of which serves to close a contact 28, and the latter to shift all the contacts of the set generally designated as 29 when the common device assumes itsposition before theiswitch 1. The contact set 29 comprises seven'sets of individual contacts of which, as shown in Fig. 2,

30 to inclusive are normally open, and

16 contact 36 is normally losed at all times except when moved to th ir alternate positions by'the pin 27 of a stepping device.

Arrangedadjacent to the shafts 1 of the entire groupoof switches and individual to each master stepping device is a set of contact strips 37. These strips are insulated from each other and may be secured in position in any. convenient manner. A set of .sbrushes 38 insulatedly mounted upon the 26 table 20, slidingly engage their respective contactstrips 37 for the purpose of conveying current to and from the operating magnets 17, 19 and 21. The contact strips 39, which are arranged between adjacent switch 80 shafts 1, serve a purpose hereinafter to be described.- Each shaft 1 also has a vertical and rotary holding ratchet 40 and 41, with which the awls 42 and 43 respectivel coact to 35 retain said shaft in its actuated position. Anendless worm 44, similar to worms 8 is mounted before the group of switches 1 to be rotated by a stepping magnet 45. A release magnet 46, mounted upon'worm 44,

' 40 and'common to all switches, acts to withdraw holdingpawls 42 and 43 when positioned before a switch that is in condition -to be released. Contact strips 47 and 48 convey current to the magnet 40. As the operation of the switches will be understood from the followin description of the circuits ii is believed a ul'ther detailed explanation thereof is unnecessary. However, reference is made to the above mentioned application 'of J. L.

50 McQuarrie, Serial No. 203,971, filed Novem- 1 her 26, 1917, wherein a complete description isgiven of the switch structure.

A" description will now be given of the operations involved in extending a telephone connection in a system where the present invention is employed. For the purpose of explanation it will be assumed that the telephone s stem illustrated in the drawings usesfin er or other preliminary switches, 69' first selectors, second selectors and connectors. 1 The switches shown and described in the drawings will be considered as used in the capacityof second selectors. According to the well-known practice of trunking, each level of trunks in a first selector leads to a is served by a number of common actuating devices.

Assume that the subscriber at substation 48, Fig. 2, desiring to converse with some,

other subscriber, removes his receiver fronu its switehhook to start the operation of a finder or line switch. Such switch, which may be included in that portion of the connection illustrated by the broken lines in the figure, opera tes in the well-known manner to connect the line' conductors 49 and 50 to the trunk conductors 51 and 52, terminating in brushes 53 and 540i a first selector switch. The subscriber now operates his sender to transmit a desired number ofimpulses to the operating mechanism of the first selector, whereby the brushes 53, 54 and 55 are moved into operative relation to the desired level 'of trunk terminals. Terminals 56, 57 and 58 may represent the first set of terminals in such level and are associated by means of trunk conductors 59, 60,61 withbrushes 4, 5 and 6 of a second selector switch,.as those shown in Fig. 1. Assume now .thatthe switch shaft 1 associated with the trunk 59, (i0, (i1 is in its normal restored position, and that .1. master sterming mechanism, such as the one shown in F ig. 2, has previously been positioned beforesuch switch in readiness to operate it as soon as it is taken for use. This being the case the pins 27 and 26 on the supporting frame 14 are holding the contacts of the set 29 and contact 28 respectively in their alternate positions, whereby contacts 30 to 35 inclusive and 28, Fig. 2, are closed, while contact 36 is open. The contact 30 by being open places'a breiilt'point in the following circuit from the test contact 62 to ground: testcontact 62, conductor 63, contact 36,- conductor 64, contact 36', conductor 65, to ground-at the off-normal contact 60.

Therefore, when the first selector switch begins its secondary or hunting movement and takes its first step onto the trunk terminals 56, .57 and 58, no guarding ground potential will be found by test brush 55 upon test terminal 58, thercbv indicating that the switch associated with the trunk 59, 60, 61 is in proper condition to be selected.

T hereupon the first selector comes to rest and extends the connection by way of trunk 150 conductors 59 and 60 to the switch shown in the drawing. A circuit is now closed for the line relay '67 from free pole of battery, upper winding of such relay,'upper.armature and contact of cut-oil relay 68, conductor 69, closed contact 30, conductors 70 and 59, terminal 56, brush 53, conductors 51 and 49, over the loop: of substation 48, conductors 50 and 52, bru's 54, terminal 57, conductors 60 and 71, closed contact 31, conductor 72, inner lower armature of cut-ofi' rela 68, lower windin of relay 67 to ground. clay 67 on attracting its armature closes a circuit for the slow relag' 73, traceable from ground, armature and rent contact of re ay 67, windin of relay 73 to the free poleof battery. he relay 73 energizes and at its righthand armature places a ground, I) the followin circuit, upon all mul t'ples of the test con switches so that any other switch testing such multi les will find the same guarded so long as re ay 73 remains energized. This circuit extends from mature and'contact o 1relay 73, conductor 74, closed contact 34, conductors 63'and 61 to test contact 58 and other multiples thereof. Thecalling subscriber, proceeding to manipulate his sender in accordance with the second digit of the called number, interrupts the above traced circuit of line' relay 67,

1 thereby causing the same to vibrate its armature a corresponding number of times. Upon the first retraction of said armature, the following circuit is closed for the slow relay 752 ground, armature and back contact of relay 67, inner left-hand armature and front contact of relay 73,- winding of relay 75 to battery and ground. Relay 75 by onergizing establishes a circuit for escape magnet .76 from und, armature and contact of relay 7 5, side-switch arm 77 and its first sition contact, winding of magnet 76 to attery and ound. 'Thefollowin circuit is also closefgimultaneously with t ie encrgization of relay 75 for the primary stepping magnet 17 of the master mechanism:

' gnamd, armature and back contact of relay 67, inner left-hand annature and front contact of relay 73, conductor 78, side-switch arm 79 and its first position contact, contact strip 80, brush 81, winding of stepping magnet 17, brush 82, contact strip 83, to battery and ground. The magnet 17 thereupon at tracts its armature 18, and through the agency of its stepping pawl and the vertical ratchet 2, steps the s Likewise, for each succeeding retraction of the line relay; 67 an impulse is sent to magnet 17 and the shaft luis elevated to position its brushes 4, 5 and -6 in operative relation to the desired level of contacts in the bank 7.

At the termination of the second series of impulses the Iinerelay 67 holds its armature -attracted, and after a sufficient period has way of actor 61 at the first selector ound, right-hand ar- 4 iaft 1 up one step.

the secondary magnet 19 of the master mechanism: ground, side-switch arm 88, contact strip89, brush 90, contact and armature of magnet 19, winding of said magnet, brush 91, contact strip 92, to battery and ground.

Upon energizing, the stepping magnet 19 at-,. tracts its. armature to automatically rotate the shaft 1, carrying the brushes 4, 5 and 6 step by step, over the trunk terminals of the selected level. Busy trunks are identified by the presence of a ground upon their test terminals. 1 the secondary off-normal contact 87. is opened, thereby opening the energizing circuit reviously traced for the escape magnet 76. f, however, the first trunk in the level, upon which the brushes 4, 5 and 6 are momentarily resting is busy, a holding circuit is establishedffor escape magnet 76 as follows: battery, winding of magnet 76, side switch arm 77 ductor 84, closed contact 32, conductor 93, test brush 6, to the grounded test terminal 94. The side switch thus remains in tion 2 and the magnet 19, by interruptin its own circuit, continues to rotate the switch until its brushes encounter an idle' trunkQ 'side'switch arm 88, contact strip 95,'brush 96, winding of magnet 21, brush 97, con tact strip 98, battery. Magnet 21 upon attracting its same to enga e the )in 23 on vertical rod 24 to move sai rod ownwardly a ainst the end of lever 25. its pivot presses against the pin 99 to engage the springs 62, 100 and 101 with their respective contacts. As seen in Fig. 2 this results in extending the trunk 59, 60, 61 through to brushes 4, 5 and 6 of the selector as soon as said selector has completed its secondar' movement. Thus the connection is exten ed-to the next switch in the train which ma be operated in the well-known manner. he shoulderedend of lever 25, against which the upper end 0' the-intermediate lever 102 normally rests, as shown in Fig. 1, ueing tilted upwardly bythe acand its;sec0nd contact, conarmature 22, Fig. 1, causos the' Lever 25 being ti ted about closed contact 35, conduction of rod 24 permits lever 102 to escape its engagement with the shouldered end of lever 25 and to rotate, by the tension of-spring 103, so that its u per end now bears against 5 the under straig t surface of said lever 25. This new position of lever 102 locks lever 25 in the position which it was actuated by magnet 21 to ho] contacts 62, 100, 101 closed durm the engaged period of the switch.

This is necessary since, as will presently ap pear, the magnet 21 soon becomes inactive after having actuated the rod 24. The above described rotation of intermediate lever 102 is made possible at this time due to the .fact

that the ratchet 41 having moved up out of contact with lever 104, the rctractile spring 105 withdraws lever 104 out of the path of said levei'102. The magnet 21 also acts upon its energization to reset the side switch to its norma position.

While the side switch is momentarily standing in position 3 before being reset by magnet 21, the following circuit is established: ground, side-switch arm 88, contact '25 strip 95, brush 96, left-hand armature and contact of relay 21, brush 106, contact strip 107, conductor 108, thence by one path to the contact apd armature of the master drive magnet 11, winding of said magnet to bat 80 tery; and by another path to the winding of cut-off relay 68, to battery. Relay 68 and magnet 11 energize inithe circuit traced. Reset-n agnet 21, which was momentarily energiged yvhile the side switch stood in position 3, does not, however, immediately deenergizc when said switch restores, but locks up, as long as slow relay 73 retains its armatures attracted, over the following circuit:

. battery, contact strip 98, brush 97, winding 40 of uragnet 21, right-hand armature and contact of said magnet, brush'109, contact strip 110, conductor 111, outer left-hand armature and front contact of relay 73 to ground. Magnet 21 by holding its armatures attracted a ords a new energizingcircuit for re lay 68 and magnet 11 during the time that slow; lay 73 is holdin its armatures in their attrac (1 position. 'I his circuit is traceable fgom ground, outer left-hand armature and front contact of relay 73, conductor 111, contact strip 110, brush 109,?!bntact and righthand armature of magnet 21, left-hand armature and contact of said magnet, brush 100, contact strip 107, coitductor 108, to magnet 11 and relny 68 as above traced.

Relay 68 by energizing, cuts off the line relay 67, and the master drive magnet 11 by energizing in the above traced circuit vibrates its armature 12 to engage ratchet 10,

and thereby rotate the endless worm 8. Bo-

tation of said worm causes thesupporting frame 14 with the master stepping magnets to move away from its operative position before the switch just actuated hnd to advance toward the next switch in the group. At

the first movement of said master device, the pins 26 and 27 permit the contacts 30 to 36 inclusive and contact 28 to assume their normal positions as shown in Fig. 2. Furthermore, the pin 20, having moved onto the strip 39, presses the same into contact with its cooperating s ring. This results in the closure of the 0 owing circuit which takes the place of the circuit previously traced from the magnet 11 and rela 68 in parallel therewith, to ground at s ow relay 73: ground, contact strip 39 and its cooperating spring, conductor 112, outer left-hand armature and back contact of relay 73, conductor 108, to magnet 11 and also relay 68. so

This circuit keeps the magnet 11 actuating and insures a complete movement of the master device to its operative position before the next switch.

If, u on the master device reaching its position before the next switch, such as the switch represented generally by the contact group 29 Fig. 2, and this switch is already actuated, the following circuit is established; from magnet 11 and relay 68 in parallel, conductor 108, outer left-hand armature and back contact of relay 73, conductor 112, to a closed contact corresponding to 28 of the set 29', a conductor similar to 113, to ground at 1 an off-normal contact 66 of the busy switch. Therefore the drive magnet 11 continues to move the master device past the actuated switch and on to. the next one in order.

Assume now that this next switch is in its normal position and has a master mechanism standing bcfore it, similar to the one illustrated diagrammatically in Fig. 2, and

which in its travel before the switches cooperates with the lower sets of contacts in that figure, such as the set 30' to 36' in elusive. In such event the master device under discussion upon arriving before such switch completes the following circuit for relay '68 and drive magnet 11: relay 68 and magnet 11 in parallel, front contact and lower armature of relay 68, conductor 114,

a closed contact similar to 33 of the set before the assumed switch, a conductor similar to 115, a closed contact similar to 33, before which there is already a master device resting, over the conductor 116', to ground at the lower armature and back contact of the cut-oil relay similar to 68 of such master device. Hence the magnet 11 continues to be energized and the master device passes 120 by said switch, which already has a master device resting before it,'-and in the manner already described goes on to the next selector switch.

If the next switch encountered is in norinal position, and has no master device already before it, then, when the Seeking mastci"dcvice assumes its position before such switch, the opcrutin circuits above described for the drive mzinct 11 and relay lector had positioned its brushes 53, 54 and 55 u on the terminals of trunk 59, 60, 61,

- it Wll be remembered the assumption was that thesecond selectorswitchassociated V .with said trunlr'wasidle and had a master 1 devicepositioned before it. If,however, the

switc is idle but has no master device assov,

ciated. therewith, it is *obvious that said switch isnot in! proper condition to be Solected and should therefore test busy to the preceding switch. This condition is obtained as follows: Since there is no master device before the switch all-of the contacts 36, 36 etc., are clo so that when brush 55 makes its test of trunk 61, a ground second.

is foundthereon. The circuit afi'ording this und is traceable from test trunk 61, conuctor 63, through'the closed contacts 36,

etc.,-in series, to ground at the oil-normal contact If the: switch had been reviously actuated and wasfbusyextend ng a call when the above mentioned test was made, a ground would'have been present on'test conductor 61 by way of. test terminal 94, brush 6 and contactY62. F rom theforegoing it is apparent, that a switch, in order to be select able to a preceding switch,'must not only be i Is and restored but must also have a In rjstepping mechanism associated there W1 1 Should, for any'f reason the subscriber abandon his call while the side switch is in position, the following circuit is closed for the-reset magnet 21. to restore the side switch to normal: ground, armature and back contact of rela. 67, inner lefthand. armature and back 'in 73, conductor 117, side-switch arm 118 and its second position contact, contact stri 119, brush 120, winding ofmagnet 21, brus 97, contact strip 98, to battery and ground. At the same-tune the fol-lowing circuit is established for the drive magnet 11.) move the master device away from the selector switch: ground at the armature of relay 67, over the circuit just traced to the brush 120, thence by way of the left-hand armature and contact of magnet 21, brush 106,

strip 107, conductor 108, magnet 11 to battrv.

Considering now the release mechanlsm,

it will be described how the magnet 46,

which is common to all switches of a group is capable of locating such switches as are inproFer condition to be returned to their norma POSltlOll. The magnet 45, which drives the worm 44, receives its ener ization over the following circuit: free )0 e of battery, winding of magnet 45, armature and contact of said magnet, contact and tact of relay armature of relay 121, to ground. Solong as relay E121 remains inert, the magnet 45 interrupting its'own circuit will drive the release magnet 46 back and forth before the switch shafts 1. Relay 121 is arranged to receive suliicient current through GSlSlr' 'ance 122 on] from groun connections. 'If magnet 46 passes before a switch that is idle the pin 124 on arm 125, by closing contact'126, Flames a ground on conductor" 123 as folows: ground, oil-normal contact 66, con-v ductors and 93, closed contact 126 to conductor 123. The-relay 121 remains deiinerglzed and magnet 45 continues .its movement, due to a closed contact 128, to the next switch position. before which the release magnet passes is being actuated a ground is extended to conductor 123 from a seoondaryoif-nonnal contact 87, aconductor similar to 86, aclosed contact similar to 35, conductors as 85 and 84, a closed contact similar to 32, a conductor similar to 93, a closed contact 126, to conductor 123, 'while said switch is inits primary movement. But if the switch is in its secondary movement, contact 87 is open, and the ground is now afl'orded from busy test. terminals 94, by way of a conductor similar to 93 to conductor 123. v

When, however, the release magnet 46 positions itself before aswitch which is idle and in condition to be restored, no short circuiting ground is present on conductor 123, and consequently relay 121 attracts its 10 armatures. This opens the circuit of magnet 45, thus stopping magnetAG noperative relationto the flange 129 of holding pawl 43, Fig. 1. A circuit is also closed for magnet 46 from ground, armature and contact 0 121, strip 130, brush 131, Winding strip 133, to buton attracts the olding dogs 42 holdin do s 42 and 43 arm from their ratchets to insure a complete restoration of 1 the shaft 1. At the same time finger 135 closes contact 136, whereupon a ground is again placed oniconductor 123, which in.

turn de energizesmelay .121, and the drive magnet operates to move the release mecha- 12 lVhen shaft 1 reaches normal the nism.

41, through the agency of lever-104,

ratchet restores levers 102 and 25 to their normal positions as shown in Fig. 1, thereby opcnmg contacts 62, 100, 101 and 130, and also unlocking holdin pawls 4i. and 43.

In describing t e features of our improved circuit arrangement we have assumed that the selective switches, in connection with which the same is used, are serving in the 1:10

when conductor 123 is free If the next switch holding capacity of second selectors. However, it is to be understood that this election is merely for the purpose of comreniently exemplifying enumerous applications contemplated 6 by the resent invcntipm. It. will be ap- "parent t the circuit arrangement. of the snid'invention is applicable to a roup' of switches employed at any partial or point inn train 'of circuit cxtendin switches, 19, PlOVi idn' Mini; made, as in he present "embodimeng \v e1 by-an switch of such 1-. group-.is-capable of vre'n ering itself non- V f selectableto thepreoeding switch or other circuitpxtending nicans during the time said 16 switchhas no com| uon' opemtin'gdmfive ap-' 'pottion'ed' thereto, or is other-\ 'ise not in pro 1' condition'to be taken for use.

. atis claimed is:. 2 p

'- -L In a. telephone systennfi telephone line,

.20 tmnlijs'clecting liican's, means for' extending saiddine thereto, ii-group of trunks tel-nugrouplo f'jswitches, each one air-manually associated;\vitl1"one;of* said trunks, a plui. 2 5 o fs'..;gunnon stepping devices, means to; mow: Y anyonethe cof into position i jnctuate an" one of said swit hes.

and means *forrendermQ-on ofs'a'id trunks i -non-'s clectzible'to saLdselcct-mg means when wilqne 'of szild devices are 'operatit'cly US$0- cw. ed-ieiththecbrl-csponding switch.

tielephone 'sysbcin; a telephone line, means; means for extend: a}:

. "said line a gronp of trunks 'tcrnnone system, a; .line, 1 trunk A v; I selectm means or extending said ltion to nllgngv n'si.;in( erftho jfoint couti'ol of said shaf ndi? ley ees for, rendering j-nating'fljin said 'trnnk" selecting means, a

switch is in its normal position but has none. of said common devices operatn'e'ly assowcialcd therewith.

5.1a a telephone system, subscribers liucs. a gioup of trunks, circuit extending means for cxtendmg'said lines to non-busy trunks .of said group, a group of switches,

each one being permanently associated with one of. said trunks, a common. stepping nua-hanism having a position for-engaging and operating each switch of said gi-oup5 nu'nns for moving said mechanismsuccessivcly from one position to another,- and means for plan-m" a bus condition upon the trunk corrcspomling to one oisaid switches when said mechanism leaves its operative position with respect to said switch, 3

6. In a telephone system, a telephonelliin c, a group 'of trunks. trunk selecting mentis' 01" connecting said line to one of said ttunksQa;

group of switchcs. each one being associated with one of said trunks, a common stepping "magnet forqictua t'ing said switches, means} for moving, said magnet into operative ciatiou with any one of said switch and means for rendering a trunk selectab e to said trunk selecting means when said mag; not isnpciatu'cly associated with the correspending: switch and Itor rendering said trunk non-selectable l. said magnet nun-cs out of operative"association tlici'ewith.

T. In a telephone si'stem. a telephone line,

a group of trunks, trunk selecting means for connecting said line to said trunks, n gi'ou of H\\lil'll(!-;. each one being associated \Ylt L (mo. of said trunks, a plurality 'of magnets common to the switches of said groiip', means for movuw an one of sanl 'ma n'ets into. position toactuate any one of said switches,

and means for reinlerim any one ofs'aid trunks oi -seleet ihle nvlien none Y of sa1d,

s-l areoperativcly associated with the correspondingswitch.

H .-'.st'em, a group of roup of' switches, each one-beingssocfi figd wi h gf id u k i "'ating magnets common to;

-h setincluding prin'iiiryfv y topping magnets an "ai gcd" [to ietiiatesaidswitches; means'for moving" anyone of said 'to'o a-rativcly associate .thesani witlnany one ofsaid sutitches, and

Y v l l menus for changing the electr cal condltiom r 0f one-of said trunkswhen'ndne of said'sets means for thereupon moving said mecha nism into osition to actuate some other switch in t group, and means to prevent said mechanism becoming associated with a switch having another common mechanism associated therewith 10. In a telephone system, a subscribers station, a group of switches, a plurality of switch actuating devices common to the switches of said group, each one being normally associated with a 'difi'erent switch, means for controlling one of'said devices from the subscribers station to move one of said switches to its actuated position, automatic means for thereupon moving said device into operative association with some other switch of the group, and means controlled by said common devices to prevent more-than one thereof becamin associated with the same switch. i

11. In a telephone system, a group of switch shafts, a. common releasing device therefor having an operative 'jposition for each of said shafts, automatic ste ping means for successively movin said evice from one position to another, and means for stopping said device in opotative relation to any one of said shafts.

12. In a telephone system, a group of switch shafts, a common release magnet having a position before each shaft for releasing the same, a stepping magnet for driving said magnet from position to position, and means for automatically arresting said release ma net in position to release a predetermined one of said shafts.

13. In a telephone system, a trunk, a switch associated with said trunk, an actu ating device for moving said switch from I'; normal to its operative position, and means controlled by said device for placin a busy condition on said trunk when said switch is in its normal position.

14. In a telephone system, incoming circuits, outgoing circuits, a plurality of switches for interconnectin said circuits, a plurality of operating mec anisms common to said switches, means for moving any one of said mechanisms into position to actuate any one of said switches, and means forrendering a switch non-selectable to an incommeans for moving any one of said devices into position to operate an one of said switches, and means for mu ering a switch ineffective to interconnect said lines when none of the common devices are in position to actuate such switch.

16. In a telephone system, subscribers lines, a group of switches for interconnecting said lines, a plurality of actuating devices common to said switches, means for moving any one of said devices into position to actuate an switch of the group, and means controlled y said devices for rendering a switch inefi'ective to interconnect said lines.

17. In a telephone system, subscribers lines, a group of switches for interconnecting said lines, a plurality of step-by-step devices common to said switches, means for moving any one of said devices into position to actuate any switch of the group, and means under the control of a subscribers line for operating said devices.

18. In a 'tele hone system, subscribers lines, a roup o switches for interconnecting said ines, a plurality of operating mechanisms common to the switches of said group, means for controlling the operation of one of said mechanisms to move a switch to its actuated position, automatic means for thereupon advancing said mechanism into position to actuate some other switch of the group, and means to prevent said mechanism becoming associated with a switch having another common mechanism associated therewith.

19. In a telephone system, subscribers its:

into position to move some other'switch'of the group.

In witness whereof, we hereunto subscribe our names this 16th day of November, A. D., 1917.

JAMES L. MoQUARRIE. CHARLES L. GOODRUM. 

